1. Field of the Invention
The present invention relates to an apparatus for adjusting the position of a cylindrical image carrier relative to a scanning head.
2. Background Information
The present invention can be applied to devices that generate images and to devices that reproduce images, in particular for the production of type forms and for the scanning of originals.
It is known for the production of type forms inside or outside of printing presses that the material to be printed, such as a printing plate, with a surface coating suitable for printing is fastened to the outer surface of a cylinder and is brought into point contact with the material to be printed by means of a tool. The tool can be designed such that multiple dots are produced simultaneously. The tool can be located on a mounting which in order to cover the entire printable area can be positioned within a longitudinal guide in the axial direction of the cylinder as the cylinder rotates. With most printing devices, optimal function of the tool may only be possible within a narrow range of tool to media distances. It is therefore known to maintain a constant distance between the tool and the cylinder. The tool can be positioned in the radial direction, the cylinder as a whole can be moved toward the tool, or both elements can be positioned simultaneously. If a light source, e.g. a laser, is used as the tool, optical elements for shaping the beam, such as autofocus systems, can be located in the light path to ensure that a constant amount of energy is applied to a constant area of the material to be printed regardless of shape and positioning errors with the cylinder and the material to be printed. Autofocus systems based on strictly optical position sensors are unreliable when used under harsh conditions such as inside a printing press. Mechanical positioning of the tool and the material to be printed can be used in combination with optical shaping of the beam.
Every degree of freedom presented by the specific application can be utilized for the mechanical positioning of the tool and the material to be printed. DD 231433 A1, for example, discloses an arrangement for positioning a wafer in a lithographic projection system in which the projection system is fixed and the wafer can be displaced in two directions and rotated around three axes. A multiplicity of travel and position measuring systems and actuators are required for positioning; this is both costly and complex.
An object of the present invention is to develop an apparatus for adjusting the position of a cylindrical image carrier relative to a scanning head that cheaply and easily permits substantially reliable positioning.
This object can be achieved by an apparatus for adjusting the position of a cylindrical image carrier relative to a scanning head, whereby the image carrier is mounted so as to be rotatable around its longitudinal axis, and wherein the image carrier is mounted such that it can be swiveled around an axis perpendicular to the longitudinal axis. The cylindrical image carrier can be positioned by means of a single swiveling movement, i.e. only a single actuator engaging at a single point is required. If the image carrier is the plate cylinder of a printing press, an existing apparatus for adjusting the diagonal or inclination register can be used as the actuator. Generally, no special actuators are required in this case.
The scanning head is a carrier for a tool for producing, modifying or erasing an image on the image carrier and/or a carrier for an element holding an image already on an image carrier. The term xe2x80x9ctoolxe2x80x9d refers to all devices suitable for producing an image, such as shaping tools, cutting tools or devices for modifying the surface characteristics of the material to be printed. One example could be semiconducting laser diodes that can be positioned substantially equidistant from one another along the surface line of a cylindrical image carrier. In this case, the semiconducting laser diodes can be moved a distance equivalent to the distance between the diodes toward the axis of the image carrier. Also suitable for use as a tool can be a single semiconducting laser that can be positioned over the length of the cylindrical image carrier, downstream of which is located a light valve arrangement facing the surface of the image carrier. It can also be possible to position the scanning head parallel to the axis of a cylinder holding an image or the material to be printed. It is also possible for the scanning head to be swivel-mounted at some distance from the image carrier, whereby the image holder or the direction of effect of the tool can be inclined toward the surface of the image carrier.
The above discussed embodiments of the present invention will be described further hereinbelow with reference to the accompanying figures. When the word xe2x80x9cinventionxe2x80x9d is used in this specification, the word xe2x80x9cinventionxe2x80x9d includes xe2x80x9cinventionsxe2x80x9d, that is, the plural of xe2x80x9cinventionxe2x80x9d. By stating xe2x80x9cinventionxe2x80x9d, the Applicant does not in any way admit that the present application does not include more than one patentably and non-obviously distinct invention, and maintains that this application may include more than one patentably and non-obviously distinct invention. The Applicant hereby asserts that the disclosure of this application may include more than one invention, and, in the event that there is more than one invention, that these inventions may be patentable and non-obvious one with respect to the other.
Advantageous embodiments of the invention are disclosed in the features.